The increased use of UHF in television broadcasting has created a need for an efficient antenna that will produce a high gain over a broad band of frequencies and will continue to do so even after a prolonged period of exposure to weather and, as well, over a wide range of elevational situations with respect to the broadcast site. Similarly, the needs for efficient reception in the VHF area have not been satisfactorily fulfilled in that, for example, many low-lying areas still encounter difficulties in the reception of VHF television signals notwithstanding their relatively close proximity to the broadcast site. Similarly, other topographical and environmental factors interfere with normal VHF reception. Accordingly, a need has long existed for an improved VHF and UHF reception antenna that can achieve a high gain over a broad band notwithstanding the elevation of placement of the antenna or other topographical factors.
The historically known style of stacking and coupling antenna elements together has restricted the number of elements which could be effectively coupled together in an array. This has been a limitation in the production of a high gain, broadband antenna in the UHF area in that UHF wave energy is readily lost, attenuated or otherwise altered at the antenna. This is particularly true at points in the antenna where the wave energy is transferred to or from feed lines through electrical contacts that may become corroded and even open during periods of extenuated use. Such changes in the conductive properties of electrical contacts after the antenna is put into operation causes the precisely established phase relationship between the coupled antenna elements to become atlered and, thereby, reduces the effectiveness of such an antenna.
An additional limitation in the prior art has been that VHF antennas have dictated one set of physical size requirements, while UHF antennas have stipulated a rather different size and design situation. Therefor, it has generally been not feasible to have in a single antenna the capability of receiving both VHF and UHF signals. In particular, in VHF reception, it is necessary to obtain an efficient induction of a tangential magnetic (or H-field) into the antenna support structure, e.g., the creation of currents in the antenna structure is necessary in order to capture the greatest possible amount of the H-field.
It is known that currents on a conducting surface are associated with an external tangential magnetic field that is maximum at the conducting surface. Such a magnetic field can generally be established and maintained more effectively by a loop element than by a stub or dipole element. However, while this has historically been recognized in the case with VHF reception, it is less established in the case of UHF reception in which the use of dipole elements is more conventional.
The prior art in this technology is represented by such patents as U.S. Pat. No. 3,434,145 to Wells and U.S. Pat. No. 3,823,403 to Walter. The pertinent area of classification is deemed to be U.S. Class 343, sub-classes 742 and 744, these sub-classes relating to high frequency type loop antennas.